1. Field of the Invention
This invention relates to the stabilization of organic polymers against the harmful degradative effects, such as discoloration and embrittlement, caused by exposure to ultraviolet light. More specifically, this invention relates to new derivatives of 2,2,5,5-tetramethylimidazolidin-4-one, a process for their manufacture, their use as light stabilizers for organic polymers, and the polymers stabilized with these additives.
2. Description of the Prior Art
It has been proposed to stabilize polymeric materials against ultraviolet light deterioration by the use of various types of ultraviolet absorbers. Thus, U.S. Pat. No. 3,004,896 discloses for this purpose 2(2-hydroxyphenyl) benzotriazole derivatives, while U.S. Pat. No. 3,189,630 discloses certain metal salts of hydroxybenzoic acids which are useful as actinic stabilizers in synthetic polymers.
Additionally, derivatives of 2,2,5,5-tetramethylimidazolidin-4-one have been disclosed as ultraviolet light stabilizers in the following: U.S. Pat. Nos. 3,532,703, 3,645,965, 3,971,757, and 3,956,310; Neth. Appln. 74-08217; Swiss Pat. No. 579,117; French Pat. Nos. 1,528,233 and 2,234,294; Danish Pat. No. 3365/74; British Pat. No. 1,453,099; German Offens. 1,817,703 and 2,500,313; and Japanese Kokais 76-26,874 and 77-27,458.
The Murayama et al. patent, 3,532,703, for example, relates to imidazolidine-N-oxides having the formula ##STR1## wherein R.sub.1 and R.sub.2, which may be the same or different, represent an alkyl group or they may be linked together with the carbon atom to which they are attached to form a saturated 5- or 6-membered homocyclic ring which may be substituted with an alkyl group or a group of the formula ##STR2## wherein R.sub.1 ' and R.sub.2 ', which may be the same or different, each represent an alkyl group or they may be linked together with the carbon atom to which they are attached to form a saturated 5- or 6-membered homocyclic ring which may be substituted with an alkyl group. These compounds are produced by treating an imidazolidine derivative having the formula ##STR3## wherein R.sub.1 and R.sub.2 are as defined above, with a peroxide. These imidazolidine-N-oxides of Murayama et al. are said to exert a stabilizing effect on polyolefins against photodeterioration. This patent corresponds to French Pat. No. 1,528,233.
A later Murayama et al. patent, 3,645,965, discloses 2,5-tri- and 2,5-tetra-substituted-4-oxo-imidazolidine compounds having the formula ##STR4## wherein the several R substituents may be many different organic radicals. A few specific representative compounds disclosed include:
2,2,5,5-tetramethyl-4-oxoimidazolidine (M.P. 169.degree.-170.degree. C.); PA1 2,5-dimethyl-2,5-diethyl-4-oxoimidazolidine (M.P. 77.degree.-79.degree. C.); PA1 2,5,5-trimethyl-2-isobutyl-4-oxoimidazolidine (M.P. 126.degree.-128.degree. C.); PA1 2,5-dimethyl-2,5-diisobutyl-4-oxoimidazolidine; PA1 1,4-diaza-2,2-dimethyl-3-oxo-spiro[4.5]decane (M.P. 193.degree.-194.degree. C.); and PA1 cyclohexane-1-spiro-2'-(4'oxoimidazolidine)-5'-spiro-1"-cyclohexane (M.P. 219.degree.-220.degree. C.).
This patent corresponds in part to German Offen. 1,817,703.
The Rasberger patent, 3,971,757, discloses a host of compounds including, for example, some alkylation products of 2,2,5,5-tetramethylimidazolidin-4-one and ethylene oxide, e.g. ##STR5## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 independently of one another each denote an alkyl group or R.sub.1 and R.sub.2 and/or R.sub.3 and R.sub.4 together with the C atom to which they are bonded form a cycloalkyl radical. Rasberger also discloses related derivatives where the substitutent at the 3-N may be, for example, --CH.sub.2 CH.sub.2 OH; --CH.sub.2 CHOH--CH.sub.3 ; --CH.sub.2 CH.sub.2 OOCCH.sub.3 ; --CH.sub.2 CH.sub.2 OOCC.sub.7 H.sub.15 ; --CH.sub.2 CH.sub.2 OOCC.sub.11 H.sub.23 ; --CH.sub.2 CH.sub.2 OOCC.sub.17 H.sub.35 ; ##STR6## --CH.sub.2 OC.sub.4 H.sub.9 ; --CH.sub.2 CH.sub.2 OC.sub.8 H.sub.17, and many others. U.S. Pat. No. 3,971,757 is believed to be an equivalent of Neth. Appln. 74-08217.
In U.S. Pat. No. 3,956,310, believed to be equivalent to Ger. Offen. 2,500,313, many N-carbamoyl imidazolidinones are described. In one preferred embodiment, the compounds have the formula ##STR7## where n may be 1 or 2; Y is 0, H, or either a straight or a branched-chain lower alkyl residue, and when n is 1, R.sub.2 is a straight or branched chain alkyl residue having from 1 to 20 carbon atoms, a straight or branched chain alkenyl residue having from 3 to 18 carbon atoms, a substituted or unsubstituted cycloalkyl residue having from 5 to 14 carbon atoms, a substituted or unsubstituted aryl residue having from 6 to 10 carbon atoms, or an aralkyl residue having from 7 to 18 carbon atoms; and when n is 2, R.sub.2 is a straight or branched alkylene residue having from 2 to 20 carbon atoms, a substituted or unsubstituted arylene residue having from 6 to 10 carbon atoms or an aralkylene residue having from 7 to 18 carbon atoms. Suitable substituents on R.sub.2 cycloalkyl or aryl residues are halogen atoms or alkyl groups having from 1 to 12 carbon atoms or alkoxy groups having from 1 to 4 carbon atoms.
French Pat. No. 2,234,294, which appears to correspond to British Pat. No. 1,453,099, and to Swiss Pat. No. 579,117, discloses compounds corresponding to the general formula: ##STR8## wherein
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 each represent, independently of each other, an alkyl radical, or each of R.sub.1 and R.sub.2, and R.sub.3 and R.sub.4, may form, together with the ring carbon to which they are bonded, a 5 to 7 carbon cycloalkyl;
Y is H or O;
n is an integer of 1 to 4, and
X may be any one of several different substituents, depending in part on the value of n. Thus, when n is 1, X may be alkyl.
Japanese Kokai 76-26,874 discloses imidazolidyl propionitriles of the general formula ##STR9## where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are hydrocarbon groups and can be the same or different, and R.sub.1 and R.sub.2, and/or R.sub.3 and R.sub.4, together with the ring carbon to which they are attached respectively, may form a cycloalkyl group.
Japanese Kokai 77-27,458 describes stabilizers for polyurethanes of the formula ##STR10## where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 have the same meanings as in Japanese Kokai 76-26,874, but may also form heterocyclic groups.